Overview
As a measure to reduce greenhouse gas emissions, the European Union proposed a ban for Mobile Air Conditioning systems of fluids having a Global Warming Potential lower than 50 (i.e. R134a and R152a), with complementary measures such as measurement of the MAC fuel consumption. This represented a challenge and an opportunity for OEMs and Mobile A/C Suppliers.
CO2-R-744, when used as a refrigerant, is the favourite candidate to replace the R-134a. Besides safety, reliability and efficiency, the present estimated additional cost, ranging from 70 up to 150 Euro with reference to the low priced car systems, represents an obstacle. Lower priced vehicles constitute up to 70% of the present EU car market, and this number will rise up to 80% with EU enlargement. A low cost and high efficiency R744 MAC will support the EU efforts to reduce the resistance to the approval of the HFC ban, allowing a rapid diffusion of the new system with the related environmental benefits and making EU industries more competitive.
The know-how developed in this project could also be transferred to other domains such as that of domestic air conditioning.
The BCOOL project formed a cluster with the project named TOPMACS focused on the development of innovative HFC free mobile air conditioning systems.
The B-COOL Project was fully devoted to the development of a low cost and high efficiency air-conditioning system based on a vapor compression cycle using CO2, identified with the acronym R-744 when used as refrigerant fluid.
The project focused, at first, on the identification of the most appropriate testing procedures to be able to qualify, in realistic way, mobile air conditioning in terms of fuel consumption and performances (thermal comfort). A specific activity was also launched to verify the safety-related issues.
The major effort was devoted to the development of the A/C systems for a Fiat Panda with automatic air conditioning and a Ford KA with manual control.
The project work was divided into seven Work Packages:
- WP1: Definition of agreed testing procedures;
- WP2: System major requirements definition;
- WP3: Design and realisation of the new systems;
- WP4: Technological validation;
- WP5: System on bench optimisation;
- WP6: On board integration and validation;
- WP7: Dissemination.
The work programme was organised following the logical steps required to develop an automotive air-conditioning system. Firstly, the reference vehicle and major system requirements are identified: target performance, cost estimation and technological aspects.
Then common and agreed assessment methods and procedures were identified, gathering all the partners’ competencies so as to make the system’s real characteristics evident and to be able to estimate the system’s true environmental impact and perceived performance.
The development of the system architecture and components represents the crucial phase of the project. Using advanced system modelling, the most suitable system architecture and component requirements were defined, taking into account the constraint of the two reference vehicles. Innovative components matching the requirements are then designed and realised, and the systems assembled and characterised. The compressors were derived from the ongoing development of the responsible tier one suppliers, as new developments are not compatible with the timing and budget of the project.
The systems were integrated in the demonstrators, tuned and tested following the procedure identified in the project.
The new systems were compared with the reference systems and with other competitor technologies in terms of environmental impact and cost.
Funding
Results
Within the B-COOL EU-funded project a R-744 air conditioning system was conceived, developed and installed on two vehicle demonstrators representative of the European A-B segment: a Fiat Panda and a Ford Ka.
The R-744 air conditioning systems have been fully characterised on bench and on board and compared with the baseline R-134a systems.
The results demonstrate that the performance issues have been solved and R-744 A/C system can achieve the same efficiency level of present R-134a systems, even if further developments and testing are required to reach the same reliability levels as with R134a systems.
The system efficiency will increase when right-sized compressors become available. The 28cc externally controlled variable capacity compressors, designed for C-segment cars, when used on small cars, as in this study, in partial load, have a lower efficiency. Those compressors can be used to validate the rest of the components, and in a first phase of R-744 system diffusion, but smaller displacement compressors (15 cc) guarantee better efficiency.
As previously mentioned, in the short term the costs will be significantly higher than the current R-134a.
If all the OEMs were to switch to R-744 technology and production volumes were to increase, the cost would likely decrease but would hardly reach the same level of R-134a system. The technical developments within the B-COOL Project have led to specific solutions for the use of this technology in small cars.
Technical Implications
The B-COOL project demonstrated that the R-744 technology for A-B segment cars seems technologically affordable even if reliability and system additional cost are still open issues that need to be further investigated.
Policy implications
Methods to assess performance, fuel annual consumption and environmental impact have been identified and they could constitute a first step for new EU standards.